The Specification Control Drawing for the Guidance & Navigation Computer Buffer Unit built by Motorola.
The Computer Buffer Unit was the part of the DTCS (Digital Test Command System) that serialized commands for uplink to the AGC (Apollo Guidance Computer) during testing. The DTCS was the uplink portion of the ACE-S/C (Acceptance Checkout Equipment - Spacecraft), which was used for testing the Command Module and Lunar Module both at the factory and on the launchpad just before launch.